"How can someone be among a religious group, and not know if God exists?"
It isn't a question of "knowing". Look at the phrasing of the question: "absolutely certain". Anybody who hasn't had a theophany who tells you he is "ABSOLUTELY certain" God exists is exaggerating. There is a difference between knowledge and faith. Believing in God without absolute certitude is faith. Believing in God with absolute certitude, without being dead, is, well, an exaggeration.
The man who has absolute certitude will not sin.
Ever.
Any more than any man will ever steal directly from his bosses' wallet when he knows that the boss is looking straight at him.
Absolute certitude means that there is not one moment of weakness.
Good post - you type faster than me! LOL
Two minds on the same track.
Shouldn't they really be called agnostics that follow a specific faith?